HereForTheBeer: Complete guess, since we don't get access to how they make these decisions:
Might have something to do with whether gOg believe that getting Connect for any particular title will actually increase the customer base. For a low-selling title, the draw might not attract enough customers to recoup the efforts to get it on Connect.
In the case of TW3, it might be that this game has already brought to gOg as many customers as it's going to get, what with the GPU tie-in and whatever other promotional doohickeys they used around release time. Granted, there are likely virtually no contract negotiation costs for this title, between CDPR and gOg... but it's also giving 'free' access to a title that's still $25 for a base game when on sale.
Hm, could be. Some clarification on the FAQ would be nice though.
triock: For The Witcher or The Witcher 2 you can use this -
https://www.gog.com/witcher/backup Thanks, that worked. Now I just need one for W3 :D